Snorkels and diving goggles have been used for decades for observing the underwater world. Still, many people know images of fish and corals only from TV or aquarium.
For snorkeling, the person wears diving goggles and a snorkel and floats in the water face-down with or without fins. In this position, the diver is 90% within or under the water. Diving suits and swimming aids reduce the immersion; the face, the ears or the entire head will always remain immersed.
To exercise this kind of diving, the person needs some practice. The diving goggles must be closely fitted to the face to avoid the ingression of water. The head strap must not be too taut or too lose. The snorkel must be in the proper position to reduce the ingression of water. When exhaling, the snorkel must be regularly blown free to keep the inhaled air flow free of water. Persons suffering from claustrophobia cannot wear diving goggles. Persons with sensible ears avoid getting their ears wet. Many people, specifically women, do not want to wet their hair or ruin it by wearing diving goggles, and to some people, the water is simply too cold to immerse therein completely.
For these reasons, diving goggles are used as a batiscope (water glasses, viewing funnel) in connection with air mattresses. In this case, the person lies on the air mattress, basking and viewing the underwater world through diving goggles which are simply held in front of the face. In this case, however, breathing without a snorkel will become a problem because the face is too deeply immersed.
Air mattresses made of a transparent sheet or having transparent portions are offered in the market. The viewing quality, however, is very low because the sheet is curved and not clear and because air bubbles form under the mattress which distort the image.
DE 203 15 281 U1 discloses an air mattress with an insertable underwater viewing unit which includes a tube insertable into a through-hole of an air mattress, a rest for a viewer's head provided at the upper end of the tube, and a transparent pane disposed within the tube.